The poll of fathers and sons found more than three quarters of dads dread the theme of sex coming up in conversation with their offspring because they find it so embarrassing to discuss.
Almost one in five even admitted to feeling uncomfortable talking about personal grooming while more than one in twenty would be stumped by the topic of car maintenance.
It also emerged one in three dads have even tried to dodge a conversation altogether by giving a vague answer or pretending not to have heard in the first place.
But despite the rise of online tutorials via YouTube and the thousands of 'how to' videos, 80 per cent of dads still see it as the father's role to talk to a son about important topics, including sex, personal appearance and relationships.
And while sons admit they would be most likely to turn to the internet for advice about sex, relationships or personal grooming, one in four still reckons their dad gives the best advice.
A spokesman for Gillette, which commissioned the research, said: "For the men of today, information is literally at their fingertips"
"At the touch of a button, smartphones serve as a gateway to countless how-to videos, resources and guides, in a matter of seconds.
"However, when it comes to advice on the more complicated issues that a young man will face, there is no better source than a dad."
The study of 1,000 fathers and 1,000 sons found 44 per cent of dads have felt uncomfortable talking to their children about certain subjects, either because they were embarrassed or felt they didn't know enough about the subject.
Sex is the theme most likely to leave fathers cringing, followed by relationships, first dates, personal hygiene and appearances.
And while 49 per cent dislike the conversations because they find it embarrassing, the majority (58 per cent) admit it's born out of worrying about their offspring's embarrassment at the discussion.
As a result of their discomfort, 32 per cent of dads have tried to dodge a conversation they would rather not have with their children, with 44 per cent of those saying they just gave a vague answer and then change the subject.
One in four just responded with an 'I don't know' while 17 per cent pretended not to hear them at all.
But 18 per cent admit their children have seen through their delaying tactics, while more than one in ten have ended up rowing with their offspring as a result.
Furthermore, one in twenty dads admitted to giving poor, or even the wrong advice on at least one occasion.
Despite this, one in three sons say their dad is the first person they turn to for advice, with one in five admitting they would be lost without the help and advice of their father.
And many acknowledge their dad gives the best advice, with almost one in four dads having taught their son how to shave.
A spokesman for Gillette added: "Ingrained in Gillette's purpose, Father's Day is a moment to celebrate fatherly advice, an integral part of a man's journey through manhood.
"Naturally, Gillette feel that they should play a role in sparking that emotional connection, bringing the father-son relationship closer together in an age where technology is so heavily depended on"
Top ten conversations fathers find most uncomfortable:
2. Relationships and marriage
3. Early dating
4. Personal hygiene
5. Personal appearance and grooming
7. Clothes and fashion
8. Work or career choices
9. Car maintenance